Catering to future mines with the right sewage plans

Many roadtrains have been around for up to 30 years and gradually upgraded to meet enlarged capacity.

Wastewater treatment expert Paul Cobbin explores three issues mining companies face — plant upgradability, expandability and water scarcity — and how to overcome them. Australian Mining writes.

Hydroflux Epco’s Paul Cobbin recalls building a water treatment plant in the Gulf Province of Papua New Guinea as a young foreman during a coup d’état in nearby Bougainville.

The plant was intended for a construction camp at a mine that had not yet been built, with only a runway already in the works.

A piece of this runway, unfortunately, knocked over the site’s only crane. The crane was key to building the water treatment plant and the only tool the foreman had to offload the fully welded tank from the truck it came in on.

“It was 1997. The camp foreman and I scratched our heads for a little while before coming up with the idea of using a Chinook two-blade helicopter to put the entire project together,” Cobbin says.

“Working in a remote site with two blades for eight hours a day in the 1990s was a little bit of hard work. But that’s the sort of things you will encounter in mines. These mine sites are very remote and our sewage treatment technology is exactly designed for that.”

Cobbin was installing the technology known as Hydroflux Epco RoadTrain, which had been used in Australia since the 1960s.

The RoadTrain package plant first sprang to life in a Bowen Basin coal mine in central Queensland. This original plant was designed for a capacity of 400 people in 1970s, but after a couple of relocations and renovation, it could accommodate up to 800 people by 2012.

This 150-cubic-metre-a-day RoadTrain was also augmented, to increase treatment quality to allow for 100 per cent effluent reuse to flush the toilets, water the gardens and wash the laundry, from the original discharge criteria of being released to the creek.

It highlights the importance of having a scalable water treatment plant that meets current and future treatment capacity, while being adjustable to the changing environmental criteria of modern times.

“The compliance requirements of the 1970s are totally different to the compliance required in 2019 – there was no way you could picture back in the 1970s what the requirements of 2019 were going to be. Who knows what will be required in 2050?” Cobbin says.

“It’s quite possible that we won’t be allowed to discharge at all – the water might need to be fully reused or even be drinkable. Whereas a camp services designer in the 1970s would likely have lost his job if he suggested reusing sewage effluent.

“So when you buy equipment now, it should not only be bought for the requirements now, but also to allow for possibilities for change. That’s what we do with the plants we put around mine sites.”

BHP Mitsubishi Alliance (BMA) has experienced repeatable success with RoadTrain since 1978 at Blackwater, according to Hydroflux.

Six welded RoadTrains are spread across BMA’s 40 kilometres of the lease, requiring only operator skills, maintenance and testing regimes for one style of process system.

Hydroflux has added equipment and technologies to the plant to complement the base structure and bring it into a new level of compliance.

As mining operations have migrated along the coal seam, so have the facilities. The toughness and ease of relocating the RoadTrain have provided economic advantages through reusing instead of replacing the asset over time.

“A classic case in point at the moment is (an open-pit copper and gold mine) in Papua New Guinea, which is putting a treatment plant for a township in the Western Province,” Cobbin says.

“Right now, in their case, we’re putting in a capacity for 1000 people. As they get their future budget, they will expand their capacity by 1000 each time. So we’re starting with the smaller component now and we’ll work on a larger component later.”

From a budget perspective, simpler technologies such as the RoadTrain are more robust but often dearer to buy upfront. However, they have a longer life and are able to withstand the harshest environments. They can be refurbished and added to while retaining their robust design, according to Cobbin.

Exotic equipment such as a membrane bio reactor (MBR), meanwhile, is cheaper to buy but is more expensive to maintain. The mass-produced technology has a shorter lifespan of about 10 to 15 years, with suitability for mines with highly-skilled operators, greater operational budget and tighter capital expenditure.

“But nobody has a glass ball to see what is going to happen in the future,” Cobbin says. “It’s constantly moving – it’s always moving – and we’re helping mine sites bring through their expansion plans.”

This article appears in the June 2019 issue of Australian Mining.

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